In a known milking system, wherein teat cups are automatically attached to the teats of a milking animal to be milked, a robot arm with a gripper is provided to grip and hold teat cups during the attachment of the teat cups. A laser emitting laser light and a video camera provided to register laser light as reflected from the teats of the milking animal are mounted on the robot arm. By aid of a method known as laser triangulation, the positions of the teats can be calculated. The movement of the robot arm can then be controlled in response to the calculated positions to be capable of finding the teats for teat cup attachments.
A drawback of such a milking system is that the camera, while being moved close to the milking animal, is exposed to dirt and possibly physical contact with the milking animal since the milking animal can make sudden movements. Further, the video camera can only be in active mode to seek for the teats when the robot arm already has collected a teat cup and initiated a movement towards the teats since the camera is fixedly mounted on the robot arm. Still further, the video camera occupies a considerable space on the robot arm, which may limit the use of the system.
In Research Disclosure, July 2002, p. 1162 is disclosed the use of an arrangement comprising a number of cameras fixedly mounted in the milking stall instead of using a video camera mounted on a movable robot arm. For instance, two or three video cameras can be mounted at each side of the milking animal to be milked, preferably on the walls of the milking stall or just outside thereof. Advantageously, the video cameras are directed diagonally upwards towards the region where the teats are when the milking animal has been positioned in the milking stall. A computer is provided for e.g. selecting two cameras, which together creates a stereoscopic image, which by means of image processing enables a substantially exact determination of the position of a teat. Two further cameras may be used to confirm the three-dimensional position of a teat. A robot arm is then moved to the teat based on the determined position.
While such an arrangement has several advantages such as a faster determination of the teats of the milking animal, a smaller and lighter robot arm, possibilities to better protect the cameras from dirt and from being damaged by kicks from the milking animal, and capabilities to monitor the complete milking operation for e.g. detecting a teat cup falling off the teat, it may be difficult to obtain a sufficiently robust, accurate, precise, and fast implementation, which is capable of controlling the robot arm to obtain a sufficiently high number of correct teat cup attachments.